Re: Atomic operations

["H. Peter Anvin" <hpa@zytor.com>]

Followup to:  <3CFBB7DB.831BE453@didntduck.org>
By author:    Brian Gerst <bgerst@didntduck.org>
In newsgroup: linux.dev.kernel
> 
> int atomic_xadd(int i, atomic_t *v)
> {
> 	int ret;
> 	__asm__(LOCK "xaddl %1,%0"
> 		: "=m" (v->counter), "=r" (ret)
> 		: "0" (v->counter), "1" (i));
> 	return ret;
> }
> 
> This one only works on 486+, but there are practically no real 386 SMP
> systems.
> 

<slaps forehead>

Boy do I feel dumb now.

The only nitpick is that it's probably better coded as:

int atomic_xadd(int i, atomic_t *v)
{
	asm volatile(LOCK "xaddl %1,%0"
		: "+m" (v->counter), "+r" (i));
	return i;
}
-- 
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